Apparatus for spray coating hollow articles



y 1966 W. A. HAZLETT 3,252,442

APPARATUS FOR SPRAY COATING HOLLOW ARTICLES INVENTOR. g1: WILLIAM AHAZLETT Fig. a. fidgfl ze his ATTORNEY May 24, 1966 W. A. HAZLETT 3,252,442

APPARATUS FOR SPRAY COATING HOLLOW ARTICLES Filed March 27, 1965 2 Sheets-Sheet 2 FF" 2 INVENTOR. WILLIAMA.HAZLETT his ATTORNEY United States Patent I O 3,252,44 APPARATUS FOR SPRAY COATING HOLLOW ARTICLES William A. Hazlett, Pittsburgh, Pa., assignor to Jones &

Laughlin Steel Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 27, 1963, Ser. No. 268,409 7 Claims. (Cl. 118-8) This invention relates to apparatus for coating the interiors of hollow articles. It is more particularly concerned with apparatus for the so-called airless spraying of coatings on metal drum shells and the like.

Steel barrels and drums for many purposes are given an interior coating of varnish or lacquer. Conventionally, the tops and bottoms of the drums are separately coated from the shell. In order to obtain a uniform coating on the interior of the drum, it is conventional to rotate the spray head and the drum shell relative to each other. If the drum shell is coated with a conventional air operated spray gun utilizing compressed air at conventional pressures, which do not exceed about 100 p.s.i., the spray may be rotated and the drum shell held stationary or vice-versa, as may be most convenient. There are, however, certain advantages in applying coatings by the so-called airless spray process, in which the coating material is projected onto the shell at high pressures, which may range from 300 to 2,500 p.s.i., or even higher. It has not heretofore been commercially practicable to provide a rotary spray head which can be fed with coating material at those pressures. The coating material must pass from the supply tank to the spray head through a rotating union of some sort, and a rotary seal which will be effective at those high pressures is an extremely expensive component.

It is desirable in the volume production of coated drum shells to rotate the spray head and hold the drum shell stationary. Such an arrangement enables the drum shells to be moved by conveyor mechanism to a spraying station one at a time, removed from the conveyor, spray coated, and returned to the conveyor, with minimum inconvenience. It is an object of my invention, therefore, to provide apparatus for airless spray coating drum shell interiors utilizing a rotating spray head, but requiring no rotary seals which must be effective at high pressures. It is another object of my invention to provide such apparatus which sprays a metered amount of coating material on each drum shell. It is another object of my invention to provide such apparatus which automatically coats each drum shell interior with the desired amount of coating material. Other objects of my invention will appear in the course of the following description thereof.

In an embodiment of my invention presently preferred by me, I position the drum shell on a non-rotating carrier or supporting means which reciprocates toward and away from a motor-driven turntable. The turntable carries the spray head, a high pressure positive displacement pump which supplies a measured quantity of coating fluid to the spray head, and a low pressure air cylinder or motor which operates the high pressure pump. The air supply to the low pressure cylinder and the coating fluid supply, also at low pressure, are connected to the apparatus on the turntable through a rotary union.

The presently preferred embodiment of my invention outlined above is illustrated in the attached figures to which reference is now made.

FIGURE 1 is an elevation partially schematic and partially in section of apparatus of my invention.

FIGURE 2 is a vertical section of a rotating union suitable for the apparatus of my invention.

FIGURE 3 is an enlarged vertical cross section through the spray head of my apparatus.

3,252,442 Patented May 24, 1966 ice The spray coating apparatus of my invention is supported on a stationary platform 1 on which is mounted a turntable 2. Turntable 2 rotates upon a plurality of bearings 3 and is constrained in a circular path by.a plurality of guide bearings 4. Turntable 2 is equipped on its bottom surface with a ring gear 5. Ring gear 5 mates with pinion 6 which is driven by electric motor 7 positioned below turntable 2 by bracket 8 attached to platform 1. On the upper surface of turntable 2 is positioned upright air cylinder or piston motor 9 with its axis on the turntable center. Air cylinder 9 is provided with a piston 10 movable therein, and connected on its bottom face to piston 11 which is smaller in diameter than piston 10, and extends through bottom 12 of air cylinder 9 and through turntable 2. On the underside of turntable 2 spray cylinder 14 is positioned co-axially with cylinder 9. Piston 11 moves in cylinder 14 and is provided with conventional means to effect a seal therewith. Piston 10 is provided with like means to effect a seal with the inside surface of cylinder 9. At its bottom cylinder 14 opens into a spray pipe 15 which extends vertically downwardly therefrom, and terminates at its bottom in spray head 16 which is equipped with a plurality of horizontally extending spray nozzles 1717. Spray head 16 is fitted with a ball 18 urged upwardly by spring 13 so as to close off the spray pipe 15 in the absence of counteracting pressure.

Positioned below turntable 2 and spaced therefrom is a platform 19 upon which drum shells are successively deposited by conveyor means not shown. At one side of platform 19 are positioned reciprocating means 20 for raising and lowering successive drum shells. Means 20 comprise a vertical column 21 provided with means not shown for raising and lowering spaced magnets 22 and 23. Those means may be a double cut screw and associated nuts, or other means which are known for this purpose. The elevating means are driven through a transmission 25 by electric motor 26. Magnets 22 and 23 are positioned to engage a drum shell 27 at two spaced areas on its outer circumference so that they support and I raise and lower a shell in contact with them. Magnets 22 and 23 are also provided with conventional means not shown for de-energizing them so as to release the drum shell.

Coating material is stored in tank 30 from which it is pumped by pump 31 through filter 32 into pipe 33 which leads to the stationary portion 34 of a rotary union 35. The stationary portion 34 is supported by bracket 36 which is attached to platform 1. The rotary portion 37 of union is mounted on air cylinder 9. The coating material from pipe 33 passes through rotary union 35 and is led out from rotary portion 37 through pipe 38, which is connected to port 39 at the lower end of cylinder 14. Port 39 is fitted with a captive ball 40 which seals off pipe 38 when the pressure within cylinder 14 is greater than the pressure in line 38.

Rotary union 35 is provided with two additional through passageways. One of these is connected through stationary element 34 with pipe 42 which leads to four-way valve 43. The other passageway connects through stationary portion 34 to pipe 44 which is also connected to four-way valve 43. Valve 43 is also connected to a compressed air line 45 which is connected to a source of low pressure compressed air not shown, and to vent pipe 46 which exhausts to the atmosphere. Valve 43 is a conventional two-position valve. In its first position it connects pipe 42 to pipe 45 and pipe 44 to pipe 46,

and in its second position it connects pipe 42 to pipe 46 and pipe 44 to pipe 45.

Pipe 42 is connected through rotaryunion 35 to pipe 48 which leads from rotary portion 37 of union 35 to port 49 in the lower end of cylinder 9. In the same way pipe 44 is connected to pipe 50 which leads from rotary portion 37 of rotary union 35 to port 51 in the upper end of cylinder 9.

Adjacent the path of travel of the drum 27 is positioned a switch 51 having a trigger 52 which is moved to actuate the switch when drum 27 starts its upward travel. Also adjacent the path of travel of drum 27 is switch 53 provided with a trigger 54 which is moved when the drum comes to the end of its downward travel. Both switches 51 and 53 are normally open, but close when their triggers move, as has been described. One contact of switch 51 is connected to line 55 which is also connected to one contact of switch 53 and to one terminal 56 of a source of control voltage, not shown. The other terminal of switch 51 is connected to conductor 58 which is connected to one terminal of solenoid 59. The other terminal of switch 53 is connected to conductor 60 which is connected to one terminal of solenoid 61. The other terminals of solenoids 59 and 61 are connected together by conductor 62 which is connected to the other terminal 57 of the source of control voltage. The movable elements of solenoids 59 and 61 are connected to four-way valve 43 so that operation of solenoid 61 moves valve 43 into its first position and operation of solenoid 59 moves valve 43 into its second position.

FIGURE 2 illustrates a commercially available rotary union which is suitable for my invention. It consists essentially of a stationary portion 34 and a rotating portion 37 which are journaled in lower anti-friction bearing 64 and upper anti-friction bearing 65. Pipe 33 is attached to stationary element 34 and opens into central passageway 66 which, through tube 67, discharges into lower passageway 68 in rotating portion 37. Pipe 67 is sealed with respect to rotating portion 37 by seal ring 69. In like manner pipe 42 opens into passageway 70 which surrounds pipe 67 in stationary element 34 and is co-axial with it. The lower end of pasageway 70 connects with bore 71 in rotating element 37 which leads to pipe 48. Passageway 70 is sealed to rotating portion 37 by sealing ring 72. Pipe 44 opens into passageway 73 which is co-axial with passageways 67 and 70 and surrounds them. The lower end of passageway 73 opens into bore 74 in rotating portion 37. Bore 74 connects to pipe 50. Passageway 73 is sealed to rotating portion 37 by seal ring 75.

The operation of my apparatus will be described with reference to the figures and foregoing description. Let it be assumed that valve 43 is in its second position, and piston is at the top of cylinder 9. Motor 7 is started causing turntable 2 to rotate. Pump 31 is started up forcing coating material from reservoir 30 through filter 32, pipe 33, and through rotary union 35 into pipe 38. The coating material from pipe 38 passes through port 39 into cylinder 14 and fills that cylinder. The free ball 40 in port 39 is forced away from the end of pipe 38 by the pressure of the coating material. Coating material also fills spray pipe 15, but spring 13 is adjusted so that it withstands the pressure generated by pump 31, and no coating material reaches nozzles 17-17.

A drum shell 27 is placed on platform 19 in position to be engaged by magnets 22 and 23. Motor 26 is started up and at the same time compressed air is admitted to valve 43 through line 45. Motor 26 drives the elevating mechanism 20 not shown and drum shell 27 is moved upwardly towards rotating spray head 16. The upper rim of shell 27 moves trigger 52, closing switch 51 which thereupon energizes solenoid 59 from the source of control voltage. Solenoid 59 in its energized condition is adapted to move valve 43 to its second position, in which it was assumed to be. Compressed air from pipe 45 passes through valve 43 into pipe 44, through the union 35 into pipe 50, and into cylinder 9 through port 51. The air beneath piston 10 exhausts through port 49, pipe 48, union 35, pipe 42, valve 43, and vent pipe 46 to the atmosphere.

The air pressure acting on the large piston 10 of cylinder 9 causes that piston to move downwardly driving piston 11 downwardly in cylinder 14 and compressing the coating material in that cylinder. Ball- 40 closes pipe 38 at port 39. The pressure in pipe 15 soon exceeds the force of spring 13, and as the bores of nozzles 1717 are small compared to the diameter of spray pipe 15, the pressure on the coating material builds up rapidly. The material is then sprayed out through nozzles 1717 as an airless spray. As drum shell 27 rises and spray head 16 rotates, the coating material is evenly distributed around the interior of shell 27. When the shell 27 reaches the top of its travel, the elevating mechanism 20 automatically reverses and brings it down again. The capacity of cylinder 14 and the air pressure applied to cylinder 9 are adjusted so that material is sprayed in a second coat as the shell 27 descends. When drum shell 27 reaches the bottom of its travel, it moves trigger 54 closing switch 53, which results in the energization of solenoid 61 from the source of control voltage. The movement of that solenoid causes valve 43 to move into its first position. In that position valve 43 causes compressed air from pipe 45 to pass into pipe 42, and from there through union 35, pipe 48, and port 49 to the bottom of cylinder 9. The air pressure raises piston 10 and piston 11 as well. Air above piston 10 exhausts through port 51, pipe 50, union 35, pipe 44, valve 43 and vent pipe 46 to the atmosphere. My apparatus is then ready for another cycle of operation.

When the pressure in cylinder 14 falls, spring 13 forces ball 18 upwardly so as to close ofi spray pipe 15. Thus, there is no drip from nozzles 1717. By adjusting the relative areas of pistons 10 and 11, the pressure under which the coating material is sprayed can be raised to the level desired for airless spraying without increasing the pressure which the seals in the rotary union 35 must withstand.

The diameter of cylinder 14 and the travel of its piston 11 are chosen or are adjusted so that the desired quantity of coating material for a drum shell is sprayed onto the shell in one cycle of operation of my apparatus. This is most conveniently done by regulating the flow of air into port 51 of cylinder 9. Although I have described a cycle of operations in which coating material is sprayed onto the drum shell while it reciprocates both toward and away from spray head 16, I can adjust my apparatus so that piston 11 completes its travel in cylinder 14 while the drum shell is being reciprocated toward spray head 16 only. Under those conditions, the coating material is sprayed onto the drum shell in a single layer.

I claim:

1., Apparatus for spray coating the interior of an open-ended shell comprising means for supporting the shell with an open end up, a turntable positioned above the shell, means for rotating the turntable about a vertical axis aligned with the axis of the shell, a spray head projecting downwardly from the turntable on its axis, means for providing reciprocating movement between the shell supporting means and the turntable adapted to move the spray head into and out of the shell, a pump mounted on the turntable adapted to discharge coating fluid at high pressure suflicient for airless spraying thereof, a motor for the pump mounted on the turntable and adapted to be operated by fluid at low pressure, a fluid connection between the pump discharge and the spray head, and a union having a rotating element mounted on the turntable, a non-rotating co-operating element, a first passageway through the union between the intake of the pump and a coating fluid supply conduit, and a second passageway through the union between the motor intake and an operating fluid supply conduit.

2. Apparatus of claim 1 including a third passageway through the union between the motor discharge and an operating fluid exhaust conduit, and a four-way valve in the operating fluid supply and exhaust conduits adapted in a first position to connect those conduits to the third and second passageways respectively through the union and in a second position to connect those conduits to the second and third passageways respectively.

3. Apparatus of claim 2 including first means actuated by movement away from each other of the shell and the spray head to cause movement of the four-way valve to its first position, and second means actuated by movement toward each other of the shell and the spray head to cause movement of the four-way valve into its second position, the first and second means being spaced from each other along the path of relative movement between shell and spray head.

4. Apparatus of claim 3 in which the pump is a metering pump adapted to discharge only enough coating 6 fluid tocoat one shell during one complete cycle of relative movement between the shell supporting means and the turntable.

5. Apparatus of claim 1 in which the pump is a piston pump and the motor is a piston motor having a piston of larger area than the piston of the pump and a stroke of the same length as the pump.

6. Apparatus of claim 1 in which the pump is a piston pump and the motor is :a piston motor having a piston of larger area than the piston of the pump and directly connected thereto.

7. Apparatus of claim 1 in which the means for providing reciprocating movement between the shell supporting means and the turntable moves the shell supporting means only.

No references cited.

DANIEL BLUM, Primary Examiner. 

1. APPARATUS FOR SPRAY COATING THE INTERIOR OF AN OPEN-ENDED SHELL COMPRISING MEANS FOR SUPPORTED THE SHELL WITH AN OPEN END UP, A TURNTABLE POSITIONED ABOVE THE SHELL, MEANS FOR ROTATING THE TURNTABLE ABOUT A VERTICAL AXIS ALIGNED WITH THE AXIS OF THE SHELL, A SPRAY HEAD PROJECTING DOWNWARDLY FROM THE TURNTABLE ON ITS AXIS, MEANS FOR PROVIDING RECIPROCATING MOVEMENT BETWEEN THE SHEELL SUPPORTING MEANS AND THE TURNTABLE ADAPTED TO MOVE THE SPRAY HEAD INTO AND OUT OF THE SHELL, A PUMP MOUNTED ON THE TURNTABLE ADAPTED TO DISCHARGE COATING FLUID AT HIGH PRESSURE SUFFICIENT FOR AIRLESS SPRAYING THEREOF; A MOTOR FOR THE PUMP MOUNTED ON THE TURNTABLE AND ADAPTED TO BE OPERATED BY FLUID AT LOW PRESSURE, A FLUID CONNECTED BETWEEN THE PUMP DISCHARGE AND THE SPRAY HEAD, AND A UNION HAVING A ROTATING ELEMENT MOUNTED ON THE TURNTABLE, A NON-ROTATING CO-OPERATING ELEMENT, AT FIRST PASSAGEWAY THROUGH THE UNION BETWEEN THE INTAKE OF THE PUMP AND A COATING FLUID SUPPLY CONDUIT, AND A SECOND PASSAGEWAY THROUGH THE UNION BETWEEN THE MOTOR INTAKE AND AN OPERATING FLUID SUPPLY CONDUIT. 